In the dark ages cats were killed off because they were associated with witchcraft. There were very few cats left in Europe to control the mice and rat populations. Poor food storage practices gave rodents easy access to stored grains. Having no natural predators and easy access to food caused the rodent population to explode. Poor hygiene and disposal of human waste into the streets allowed for easy transmission of disease to the food storage areas by the rodents. This is what caused the black death (bubonic plague) to wipe out 60% of Europe.

Cats are essential for preventing pandemics in poor counties as well as post collapse societies.

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